<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>Document</title>
	<style>
		@media screen and (min-width: 800px) {
			p{
				font-size: 400%;
			}
		}
		@media screen and (max-width: 500px) {
			p{
				font-size: 20%;
				background: red;
			}
		}
	</style>
</head>
<body>
	<p>
		哈哈哈
	</p>
</body>
</html>